The evoked EMG response commonly decreases in amplitude during the first few minutes of anaesthesia. The purpose of this study was to determine if a relationship exists between changes in hand temperature, which are known to occur with induction of anaesthesia, and drift in the EMG 94,7 5= 8,5% (~cart, 83-111%

SummaryRecent published data suggest that despite apparently satisfactory recovery from nondepolarising block (train-of-four In a recent communication, Shorten and Ali [I] reported that, following apparently satisfactory antagonism of nondepolarising block, even very small doses of additional relaxant may re-establish significant paralysis. They antagonised pancuronium-induced neuromuscular block with neostigmine and allowed recovery to proceed to a train-of-four (TOF) fade ratio of >0.90. At that point, they gave atracurium 75 pg.kg-', a dose that under normal circumstances represents little more than an EDos; 50% twitch depression quickly ensued.This finding has several implications. Firstly, care should be taken when neuromuscular block must be re-established shortly after what appears to be essentially complete return of neuromuscular function. Secondly, return to a TOF fade ratio of 0.90 may still indicate a significant reduction in the neuromuscular junction's 'margin of safety'.Unfortunately, Shorten and Ali's report is difficult to interpret. It is possible that their observation merely represents a special case-a synergistic interaction between a steroidal agent (pancuronium) and a benzylisoquinoline derivative (atracurium). It is also unclear what effect, if any, the administration of an anticholinesterase antagonist had on the observed drug interaction. If recovery to a TOF ratio > 0.90 had been allowed to occur spontaneously it is possible that the observed decrease in dose requirement might have been much reduced. We undertook the present study to investigate these issues and to quantify any change in dose requirement of a muscle relaxant when given on a second occasion after return of the TOF ratio to 0.95. MethodsTwelve patients ASA 1 or 2, aged 18 to 65 years undergoing elective surgery were studied. All patients were free from neuromuscular disease and were within 15% of ideal body weight.

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